<!DOCTYPE html>
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
  <style>
      .box1{
          width:300px;
          height: 300px;
          background-color: antiquewhite;
          padding: 10px;
          border:1px solid red;
          float: left;
      }
      .box2{
          width:300px;
          height: 300px;
          background-color: #ccc;
          padding: 10px;
          border:1px solid red;
          float: left;
      }
      .box3{
          width:300px;
          height: 300px;
          background-color:aqua;
          padding: 10px;
          border:1px solid red;
          /*float: left;*/
          clear: left;/* 清除左侧浮动：box3的左侧不允许有浮动元素 */
      }
  </style>
 </head>
 <body>
    <div class="box1">
        box1
        box1
    </div>
    <div class="box2">
        box2
    </div>
    <div class="box3">
        box3
    </div>
 </body>
</html>
